This invention relates to rotary motion control based on sensing rotary acceleration and in particular to a safety brake mechanism.
Equipment consoles for housing electronic test equipment or computer-display equipment often have a horizontal shelf for holding a keyboard and other operator interface controls or display equipment. Such a shelf may be adjustable in the vertical direction and such adjustment is usually manual by releasing a latch and lifting or lowering the shelf on rolling bearings. One example of an equipment console for an air traffic control application has an equipment shelf plus other associated moving parts weighing approximately 125 lbs. This shelf is counterbalanced to within 5 lbs. to minimize operation effort and has a vertical travel length of 10 inches. Considerable energy is stored in this shelf system due to the large weight operating over the large travel range. At the upper position, the shelf mass has potential energy due to its elevation; at the lower position the counterbalance has the same amount of energy stored up in order to help lift the shelf when required. Both types of stored energy are a hazard to operating personnel if the mechanism fails or is misused.
A sudden unexpected shelf motion can result from three sources such as counterbalance spring breakage, overloading the shelf or by removing part or all of the mass of the shelf by disassembly. Each of these conditions cause a force imbalance, which if released would result in rapid movement and potential operator injury. The release of the unbalanced force could occur by latch failure or by unintentional manual latch operation. Therefore, it is very desirable to limit shelf speed to a safe value with a safety brake. Such a brake has to be relatively inexpensive, reliable and contribute only negligible drag during normal shelf operation, and the brake engagement must occur for movement in either direction.